This invention relates to a machine and a method for packaging articles, in particular a “flow packing” machine.
In the technical sector concerned, flow packing machines are known which comprise a sealing unit, or sealing head, designed to seal an article wrapped in a film of packaging material.
The sealing head is equipped with a pair of sealing elements which are movable relative to each other to seal the film around the product.
Usually, these machines comprise a first drive motor to move the sealing head and a second drive motor to move the sealing elements relative to each other.
In a first type of machine, the first and second drive motors are associated with, or mounted on, the sealing head.
That means the weight of the sealing head is increased.
One disadvantage of machines of this type, therefore, is that the sealing head is very heavy, creating particularly high inertia loads which prevent the machine from reaching high speeds and limiting machine operation.
To overcome these drawbacks, constructional solutions have been proposed which involve fixing the first and second motors to the machine frame.
One example of such a solution is known from patent document WO97/38905 which describes a packaging machine in which the drive motors of the sealing head and sealing elements, respectively, are both fixed to the frame.
This constructional solution, however, is particularly complicated because it involves providing a plurality of gearboxes to transmit motion from the motor (fixed to the frame) to the sealing elements.
In actual fact, therefore, this machine is highly complicated and relatively unreliable in operation because drive is transmitted from the motor to the sealing elements through a plurality of parts.
Moreover, this machine does not allow reaching high operating speeds because the inertias in play, inevitably due to reversal of motor drive direction and to the kinematic structure of the transmission means, are particularly high.
Further, the machine is relatively inflexible and requires very long times for adjustment and changeover.